First of all, create-react-app is an amazing kit. It's a zero configuration bundle that gives you a react app boilerplate with a dev server, linting and a deployment tool. All are awesome but not perfect.
I could go on giving this project praise but if you're here reading this you might be convinced already.
Anyway, the way you deploy a create-react-app project is actually stunningly simple, but there is one major caveat to look out for. Basically running yarn run build will first delete existing files in the ./build/ directory. Files that it indents to replace. For example your ./build/index.html or your ./build/static/js/main.94a86fe3.js.  
So, what I suggest is that you deploy it like this:
#!/bin/bash # Go into the project where the package.json exists cd myproject # Upgrade any libraries yarn # Use yarn run build mv build build_final
Note! This tip is only applicable if you deploy "in place" as opposed to building a whole new container/image and swapping an old container/image for a new one.
Now, for your Nginx point to the ./build_final directory instead. For example:  
# /etc/nginx/sites-enabled/mysite.conf
server {
    server_name mydomain.example.com;
    root /full/path/to/myproject/build_final;
    location / {
        try_files $uri /index.html;
        add_header   Cache-Control public;
        expires      1d;
    }
}
The whole point of this tip is that it's a good idea to not point Nginx to the ./build directory (but to a copy of it instead) because otherwise, during the seconds that yarn run build runs (1-5 seconds) a bunch of files will be missing and Nginx will send 404 errors to the clients unlucky enought to connect during the deployment.
Comments
Thank you so much for this post.
I tried the same thing but actually I configured many servers in Nginx so I cont specify the root inside the location like
server{
server_name example.com;
location /reactApp/{
proxy_pass http://127.0.0.1:3000/;
root /home/tech/React_App/elasticsearch/build/;
index /home/tech/React_App/elasticsearch/public/index.
}
}
but I am getting white screen in the browser while opening on URL("https://example.com/reactApp/") the problem is it was not rendering the root